I'm not doing anything remotely scientific, actually it's closer to Literature... so I don't know if it compares, but at the moment the best I can do is 40 to 50 pages of close-reading per day. It's not as much as it sounds because some passages are not at all relevant for my thesis so I only make very basic notes for these, but still, I actually think it's a LOT. It drains all the energy out of me, and by the evening my eyes feel like they're burning. I think I'll need glasses before I know it. I'm just forcing myself a bit because I want to be done by Christmas with a pile of books I have to read first - they're all between 400 and 700 pages :p